We had popcorn ceilings in our last house. That was one of things I least liked about the house. If popcorn ceilings haven't been painted, you can't wash them. They will crumble & fall off when you get them wet. Also, they fall off if you bump them dusting them.

I considered wetting and scraping them off, but it was too big a job with cathedral ceilings.

I personally think the only way to clean them, is to paint them...and that's a job because of the deep texture.

Who ever invented popcorn ceilings ought to be shot. I hated them with a passion!!! What I did was get an old sheet and lay it over the stove and counters and got a broom and went back and forth getting the dirt, tiny cobwebs and dust off. Sure, the popcorn came off but at least my ceilings were cleaner. For grease stains on the ceilings, I used Pine-Sol with a rag and gently dabbed at it. I did it this way for the rest of the rooms. Just layed out old sheets to catch all the popcorn that came off while brushuing with the broom. It wasn't a perfect job, but it did look better. In the new house we built, the first thing I wanted to make sure of, that there were to be no popcorn ceilings!

He had too much texture left over and, to get creative, he put GLITTER in it. What the heck? Nasty stuff. I scraped our ceilings off and retextured and painted. Never again, I still have a bum elbow almost 20 years later. Popcorn ceilings will kill any sale of a house I look at to buy.